cfq: fix IOPRIO_CLASS_IDLE accounting

Spotted by Nick <gentuu@gmail.com>, hopefully can explain the second trace in
http://bugzilla.kernel.org/show_bug.cgi?id=9180.

If ->async_idle_cfqq != NULL cfq_put_async_queues() puts it IOPRIO_BE_NR times
in a loop. Fix this.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

@@ -2068,9 +2068,10 @@ static void cfq_put_async_queues(struct cfq_data *cfqd)
 			cfq_put_queue(cfqd->async_cfqq[0][i]);
 		if (cfqd->async_cfqq[1][i])
 			cfq_put_queue(cfqd->async_cfqq[1][i]);
-		if (cfqd->async_idle_cfqq)
-			cfq_put_queue(cfqd->async_idle_cfqq);
 	}
+
+	if (cfqd->async_idle_cfqq)
+		cfq_put_queue(cfqd->async_idle_cfqq);
 }
 
 static void cfq_exit_queue(elevator_t *e)